* Corresponding authors

^a Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, P. R. China
E-mail: nianli@m.scnu.edu.cn, guofu.zhou@m.scnu.edu.cn

^b National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou 510006, P. R. China

^c Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA
E-mail: ajen@uw.edu

^d Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, P. R. China
E-mail: psjwchen@scut.edu.cn

^e Department of Physics and Astronomy, and Collaborative Innovation Center of IFSA (CICIFSA), Shanghai Jiaotong University, Shanghai 200240, P. R. China
E-mail: fengliu82@sjtu.edu.cn

^f Materials Sciences Division, Lawrence Berkeley National Lab, Berkeley, CA, USA

^g Department of Chemistry, City University of Hong Kong, Kowloon, Hong Kong, SAR, P. R. China